The propagation of inverted Neel wall sections instead of magnetic bubbles in a serial access memory system was first proposed by L. J. Schwee in the publication "Proposal on Cross-Tie Wall and Bloch Line Propagation In Thin Magnetic Films," IEEE Transactions on Magnetics, MAG 8, No. 3, pp. 405-407, September, 1972. Such a memory system utilizes a ferromagnetic film of 81% Ni-19% Fe of approximately 300 angstroms (A) thick in which cross-tie walls can be changed to Neel walls and Neel walls can be changed to cross-tie walls by applying appropriate fields. Associated with the cross-tie wall is a section of inverted Neel wall that is bounded by a cross-tie on one end and a Bloch-line on the other end.
In such a cross-tie wall memory system, information is entered at one end of the serial access memory system by the generation of an inverted Neel wall section that is representative of a stored binary 1 and a non-inverted Neel wall section that is representative of a stored binary 0, and is moved or propagated along the cross-tie wall by the successive generation (and then the annihilation) of the inverted Neel wall sections at successive memory cells along the cross-tie wall. In the D. S. Lo, et al., patent application Ser. No. 495,971, filed Aug. 9, 1974, now U.S. Pat. No. 3,906,466 there is disclosed a propagation circuit for the transfer of inverted Neel wall sections at successive memory cells along the cross-tie wall. In the L. J. Schwee U.S. Pat. No. 3,868,660 and in a Naval Ordnance Laboratory Report NOLTR 73-185, L. J. Schwee, et al., there have been published some recent results of the further development of cross-tie wall memory systems and of detectors for the readout of the binary information that is stored therein.